No, only naturally aspirated cars are allowed in SP8. The GT-Rs are turbocharged and therefore in SP8T. However, you are right in terms of speed, the LFA (quickest lap: 8:34.416) seems a lot faster than the GT-R (quickest lap: 8:59.226).
You can find the complete race results by classes here:
http://www.vln.de/includes/download.php?file=../ergebnisse/2011-06-11k.pdf